Relative biological effectiveness and cell-killing efficacy of continuous low-dose-rate 125I seeds on prostate carcinoma cells in vitro.

The aim of this study was to determine the effects of (125)I seeds on prostate carcinoma (PC3) cells. The relative biological effectiveness of (125)I seeds on PC3 cells with respect to (60)Co gamma rays was 1.4. Both 4 Gy of (60)Co gamma ray and (125)I seed irradiation increased the percentage of cells in G(2) phase, but there was no significant difference between these 2 types of radiation. Significantly, (125)I seeds induced higher apoptotic rates of PC3 cells compared with (60)Co gamma ray irradiation. Furthermore, Bcl-2 expression, but not caspase-3 activity, in PC3 cells was downregulated after irradiation with (125)I seed or (60)Co gamma rays.